In plain sight? (WHY YES !??)
Apparently too many people were abusing the priviledge that DCL was allowing (against policy) so they decided to start enforcing the policy. It was reported here in October that DCL had started enforcing it.
http://www.disboards.com/showthread.php?t=3011296&highlight=rolling+cooles.
As to whether DCL should have sent the information to everyone who was holding a reservation at the time they decided
to enforce the policy, it's not really up to them to do so. And the CMs waving you on, that wasn't their position to tell you no. Now, if you had asked (??!!), they most likely would have told you that you wouldn't be able to bring it onboard.
It's always up to the cruiser to keep abreast of any rules/policies regarding their cruise (not just DCL).
(oh...I asked my TA and she said it was fine !) Things change all the time.